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GSI Field Methods and Procedures February 14, 1995 Field Screening of Soil Samples A PID is used to perform head-space screening in the field for the presence of organic vapors from the soil sample This test procedure involves removing soil from the tip of the sampling device or sample liner into a clean glass far, and immediately covering the far with aluminum foil secured under a ring-type threaded ltd After approximately twenty minutes, the foil is pierced and the atmosphere within the jar tested using a PID Head-space screening results are recorded on the boring log. Head-space screening procedures are performed and results recorded as reconnaissance data. GSI does not consider field screening techniques to be verification of the presence or absence of hydrocarbons Construction of Monitoring Wells Monitoring wells are constructed in the exploratory soil borings with Schedule 40 polyvinyl chloride (PVC) casing All points are thread loaned, no glues, cements, or solvents are used in well construction The screened interval is constructed of machine-slotted PVC well screen which extends from the total well depth to a point above the groundwater An • appropriately-sized graded sand is placed in the annular space adjacent to the entire screened interval A bentonite seal is placed in the annular space above the sand, and the remaining annular space is sealed with neat cement or cement grout Wellheads are protected with water-resistant traffic-rated vault boxes placed flush with the ground surface The top of the well casing is sealed with a locking waterproof cap A lock is placed on the well cap to prevent vandalism and unintentional introduction of materials into the well Water Level Measurements The top of the newly-installed well casing is surveyed by a California-licensed Land Surveyor to mean sea level (MSL) Depth-to-groundwater, floating product thickness, and total well depth of the well are measured from the top of the well casing with an electronic water-Ievel indicator Depth-to-groundwater is measured to the nearest 0 01-foot, and referenced to MSL The presence of floating product is confirmed using a clean acrylic or polyvinyl chloride (PVC) baiter, measured to the nearest 0 01 foot with a decimal scale tape Well Development and Sampling The purpose of well development 1s to improve hydraulic communication between the well and the surrounding aquifer. Newly constructed wells are allowed to stand a minimum of • 48 hours before development to allow the well seals to cure Prior to development, each well A-2 GeoStrategies Inc. r i